1. Field of the Invention
The present invention relates to a technique for controlling the behavior of a fluid in a vacuum chamber used in a manufacturing process with a vacuum control valve.
2. Description of the Related Art
A semiconductor manufacturing process includes a process of disposing a wafer W inside a vacuum chamber 710 (see FIGS. 1, 2) and exposing a processing surface Ws of the wafer W to a processing gas (also referred to simply as gas in this specification), as in chemical vapor deposition (CVD), for example. The processing gas contains a thin film forming element and reacts on the processing surface Ws to form a film material.
The processing gas must be supplied to the wafer W evenly and with stability in order to form the film evenly. In a conventional CVD process, however, one configuration as shown in FIGS. 1 and 2 is employed such that discharge is performed by a vacuum pump while supplying the processing gas. During this discharge control, a conductance of an exhaust system is typically manipulated using a pendulum type valve, an opening/closing amount of which is manipulated by moving a pendulum 720 as disclosed in Japanese Patent Application Publication Laid-open No. 2009-117444.
With this method, however, when a position of the pendulum 720 is moved in order to adjust the conductance, a center of an opening portion moves together with the pendulum 720. When the center of the opening portion moves in this manner, bias is generated between gas flows FL1, FL2 through the interior of the vacuum chamber 710, leading to unevenness in the gas supply such as the formation of a stagnation region in which the gas supply is disrupted, for example.
Moreover, in another configuration where the gas is supplied from one side of the wafer W and discharged from the other side of the wafer W, this unevenness in the gas supply occurs as a reduction in a concentration of the thin film forming element in the vicinity of the exhaust side of the wafer W. This bias in the gas supply generates unevenness in a film thickness on the processing surface Ws, and this phenomenon becomes gradually more apparent with increases in the precision and density of products such as that described above.